Experimental study on mixing effect of falling film on coated division tube by thermal tracing technique

Experimental investigations have been carried out for liquid films flowing on the vertical coated division tube. A new thermal tracing technique was developed to measure the mixing effect and liquid film velocity of falling liquid film on the coated division tube. In general, mixing of solution could refresh the interface of bulk liquid, and hence lead to the more efficient heat transfer within the liquid film. By using the high speed video camera and thermal imaging technique, the flow patterns and mixing effect of liquid film on the coated division tube were investigated experimentally. Flow visualization experiments revealed that the liquid film formed a bifurcate flow at the upper edge of the vertical coated regions. The bifurcate flow converged and resulted in stronger mixing that drove the thermal tracing liquid particles from the interface to the internal of liquid film. There was deformation of temperature distribution on the coated division tube. The average mixing intensity on the coated division tube was about 1.2 times larger than that on the bare brass tube.